feat(firebase): integrate Firebase + APNs/FCM push notifications

Phase 2 of multi-environment setup. Adds Firebase core, Crashlytics,
Analytics, Remote Config, Performance, Messaging and flutter_local_notifications,
plus full APNs configuration for iOS push.

- Wire setupFirebase(env) and setupNotifications() in initApp
- Add firebase_options for dev and staging via flutterfire (sf-platform-pre)
- Register google-services / firebase-perf / crashlytics gradle plugins
- Add per-flavor GoogleService-Info.plist with Build Phase script that
  copies the right plist into the .app bundle based on \$CONFIGURATION
- Bump iOS deployment target 13.0 -> 15.0 (required by firebase_analytics)
- Pin flutter_local_notifications to ^19.4.2 (v20+ needs Dart SDK >=3.10)
- Add aps-environment to staging (development) and production entitlements;
  development flavor intentionally excluded (no App Store Connect entry)
- Fix AppDelegate.swift to call super.application after forwarding to
  AntelopAppDelegate, otherwise Firebase Messaging swizzling breaks and
  the APNs token is never captured
- Crashlytics reports in all builds (debug + release) for early detection
- Tag analytics events with env user property per flavor
- App Check intentionally not included (debug-token friction with large
  QA team); can be re-added release-only later

apps/mobile_app/android/app/build.gradle.kts

@@ -3,6 +3,11 @@ import java.io.FileInputStream
 
 plugins {
     id("com.android.application")
+    // START: FlutterFire Configuration
+    id("com.google.gms.google-services")
+    id("com.google.firebase.firebase-perf")
+    id("com.google.firebase.crashlytics")
+    // END: FlutterFire Configuration
     id("kotlin-android")
     // The Flutter Gradle Plugin must be applied after the Android and Kotlin Gradle plugins.
     id("dev.flutter.flutter-gradle-plugin")

apps/mobile_app/android/app/google-services.json

@@ -0,0 +1,48 @@
+{
+  "project_info": {
+    "project_number": "535646668726",
+    "project_id": "sf-platform-pre",
+    "storage_bucket": "sf-platform-pre.firebasestorage.app"
+  },
+  "client": [
+    {
+      "client_info": {
+        "mobilesdk_app_id": "1:535646668726:android:c3a09d6c26f0cdf95e6317",
+        "android_client_info": {
+          "package_name": "com.savefamily.app.dev"
+        }
+      },
+      "oauth_client": [],
+      "api_key": [
+        {
+          "current_key": "AIzaSyAzo8E_L6iUYWmK1BDFpNqRri1df6CqJiY"
+        }
+      ],
+      "services": {
+        "appinvite_service": {
+          "other_platform_oauth_client": []
+        }
+      }
+    },
+    {
+      "client_info": {
+        "mobilesdk_app_id": "1:535646668726:android:b87245b807258e3e5e6317",
+        "android_client_info": {
+          "package_name": "com.savefamily.app.stag"
+        }
+      },
+      "oauth_client": [],
+      "api_key": [
+        {
+          "current_key": "AIzaSyAzo8E_L6iUYWmK1BDFpNqRri1df6CqJiY"
+        }
+      ],
+      "services": {
+        "appinvite_service": {
+          "other_platform_oauth_client": []
+        }
+      }
+    }
+  ],
+  "configuration_version": "1"
+}